This invention relates generally to the field of telecommunications and more particularly to a method and system for providing a protection path for connection-oriented signals in a telecommunications network.
Telecommunications systems generally operate in either a connection-oriented mode or a connectionless mode. In a connection-oriented mode of operation, signals are communicated over specified paths from a source network element to a destination network element. Connection-oriented signals include, for example, Multi-Protocol Label Switching signals with Asynchronous Transport Mode (ATM), frame relay, or packet-over-SONET encoding.
When a failure occurs along the specified working path in connection-oriented communication, the signals must be re-routed to the destination network element along another available path. Previous attempts to provide for the delivery of connection-oriented signals via an alternate route have included global repair, per-area repair and local repair.
For global repair, the node closest to the failure generates failure notification messages that are delivered to the source network element. The source network element then switches the signals to a protection path. Bandwidth is reserved on the protection path in an amount equal to the working path bandwidth.
Using a global repair scheme, however, may result in time limits for recovery being unmet due to long distances between the point of failure and the source network element. In addition, the node detecting the failure needs a way to send a reliable failure notification message to each source network element that is affected by the failure. Also, the failure notification message must be understood by the source network element. However, using global repair across different routing areas may prevent the source network elements from understanding the failure notification messages. Using global repair also results in the reservation of protection path bandwidth that prevents other traffic sources from using an optimal path, thereby reducing the total network efficiency.
For per-area repair, protection switching is isolated to a single area of network elements. However, this type of repair wastes bandwidth and results in an increased number of paths that must be maintained. In addition, per-area repair requires the use of two border nodes at every border between two different areas.
For local repair, protection switching is initiated by a node adjacent to the failure. Thus, for example, local repair schemes may include deflective routing. However, the use of local repair fails to provide for bandwidth reservation for general topologies to guarantee bandwidth for protected traffic.
In accordance with the present invention, a method and system for providing a protection path for connection-oriented signals in a telecommunications network are provided that substantially eliminate or reduce disadvantages and problems associated with previously developed systems and methods. In particular, reflectors are used to provide a plurality of segments for a protection path, thereby reducing overall packet delay and satisfying Quality of Service requirements.
In one embodiment of the present invention, a system is provided for providing a protection path for connection-oriented signals in a telecommunications network comprising a plurality of nodes. The system includes a source node, a destination node and a penultimate node. The source node is operable to transmit traffic. The destination node is operable to receive traffic from the source node. The penultimate node is operable to receive traffic from the source node, to transmit traffic directly to the destination node, to designate one of the nodes as a reflector and to generate a first segment of a protection path from the penultimate node through the reflector to the destination node.
In another embodiment of the present invention, a node is provided in a telecommunications network. The node includes an ingress port, a reflector identifier, a protection path generator, and an egress port. The ingress port is operable to receive traffic. The traffic comprises a working path, a protection path, working traffic and protection traffic. The reflector identifier is operable to identify the node as a reflector based on the received traffic. The protection path generator is operable to generate a protection path based on an identification of the node as a reflector. The egress port is operable to transmit traffic.
Technical advantages of the present invention include providing an improved method for providing a protection path for connection-oriented signals in a telecommunications network. In particular, a penultimate node in the working path designates a reflector and generates a segment of a protection path from the penultimate node through the reflector to the destination node. The reflector then generates another segment of the protection path. Accordingly, the protection path comprises a plurality of segments each operable to provide protection for a distinct protection domain. As a result, protection capability and flexibility is increased, protection switching delays are decreased, and network efficiency is improved.
Other technical advantages of the present invention include providing a method for generating a protection path for a packet-switched network. In particular, a plurality of segments making up a protection path are generated by nodes in the working path. As a result, a protection path is provided for a packet-switched network without the need for each node detecting a failure to generate failure notification messages for the source network element. In addition, network elements need not be partitioned into different protection areas.
Other technical advantages will be readily apparent to one skilled in the art from the following figures, description, and claims.